In various manufacturing operations it is standard to coat a web substrate, typically of paper, with a thick layer of a liquid that is subsequently dried and hardened, and to control the thickness of the liquid layer by passing the web through a doctor assembly before the liquid dries. In this doctor assembly a doctor rod is held at a meticulously controlled spacing from the surface of the coated web so that it strips off excess liquid and leaves the web with a coating of the exact required thickness.
German patent documents 2,410,875 of Kreienbrink, 3,022,955 and 3,620,374 of Pullinen, and 3,934,418 of Beisswanger as well as German utility models 8,232,839, 9,103,571, and 9,112,032 and copending and commonly owned U.S. patent application Ser. No. 08/140,125 of Meyer describe various doctor assemblies that function as described above. In such systems it is standard to provide an elastic mounting for the doctor rod in the form of an inflatable hose braced between a back face of a holder beam carrying the rod and a front face of a stationary support. Such a system is not ideal at high web speeds since the hose cannot itself exert sufficient force to achieve the desired tight control.